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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Pablo Neira Ayuso <pablo@netfilter.org>
Subject: [PATCH 5.15 123/244] netfilter: nf_tables: use READ_ONCE and WRITE_ONCE for shared generation id access
Date:   Tue, 23 Aug 2022 10:24:42 +0200
Message-Id: <20220823080103.171945337@linuxfoundation.org>
In-Reply-To: <20220823080059.091088642@linuxfoundation.org>
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From: Pablo Neira Ayuso <pablo@netfilter.org>

commit 3400278328285a8c2f121904496aff5e7b610a01 upstream.

The generation ID is bumped from the commit path while holding the
mutex, however, netlink dump operations rely on RCU.

This patch also adds missing cb->base_eq initialization in
nf_tables_dump_set().

Fixes: 38e029f14a97 ("netfilter: nf_tables: set NLM_F_DUMP_INTR if netlink dumping is stale")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/netfilter/nf_tables_api.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -837,7 +837,7 @@ static int nf_tables_dump_tables(struct
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
-	cb->seq = nft_net->base_seq;
+	cb->seq = READ_ONCE(nft_net->base_seq);
 
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (family != NFPROTO_UNSPEC && family != table->family)
@@ -1626,7 +1626,7 @@ static int nf_tables_dump_chains(struct
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
-	cb->seq = nft_net->base_seq;
+	cb->seq = READ_ONCE(nft_net->base_seq);
 
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (family != NFPROTO_UNSPEC && family != table->family)
@@ -3054,7 +3054,7 @@ static int nf_tables_dump_rules(struct s
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
-	cb->seq = nft_net->base_seq;
+	cb->seq = READ_ONCE(nft_net->base_seq);
 
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (family != NFPROTO_UNSPEC && family != table->family)
@@ -4036,7 +4036,7 @@ static int nf_tables_dump_sets(struct sk
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
-	cb->seq = nft_net->base_seq;
+	cb->seq = READ_ONCE(nft_net->base_seq);
 
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (ctx->family != NFPROTO_UNSPEC &&
@@ -4964,6 +4964,8 @@ static int nf_tables_dump_set(struct sk_
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
+	cb->seq = READ_ONCE(nft_net->base_seq);
+
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (dump_ctx->ctx.family != NFPROTO_UNSPEC &&
 		    dump_ctx->ctx.family != table->family)
@@ -6796,7 +6798,7 @@ static int nf_tables_dump_obj(struct sk_
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
-	cb->seq = nft_net->base_seq;
+	cb->seq = READ_ONCE(nft_net->base_seq);
 
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (family != NFPROTO_UNSPEC && family != table->family)
@@ -7728,7 +7730,7 @@ static int nf_tables_dump_flowtable(stru
 
 	rcu_read_lock();
 	nft_net = nft_pernet(net);
-	cb->seq = nft_net->base_seq;
+	cb->seq = READ_ONCE(nft_net->base_seq);
 
 	list_for_each_entry_rcu(table, &nft_net->tables, list) {
 		if (family != NFPROTO_UNSPEC && family != table->family)
@@ -8612,6 +8614,7 @@ static int nf_tables_commit(struct net *
 	struct nft_trans_elem *te;
 	struct nft_chain *chain;
 	struct nft_table *table;
+	unsigned int base_seq;
 	LIST_HEAD(adl);
 	int err;
 
@@ -8661,9 +8664,12 @@ static int nf_tables_commit(struct net *
 	 * Bump generation counter, invalidate any dump in progress.
 	 * Cannot fail after this point.
 	 */
-	while (++nft_net->base_seq == 0)
+	base_seq = READ_ONCE(nft_net->base_seq);
+	while (++base_seq == 0)
 		;
 
+	WRITE_ONCE(nft_net->base_seq, base_seq);
+
 	/* step 3. Start new generation, rules_gen_X now in use. */
 	net->nft.gencursor = nft_gencursor_next(net);